Implantable electrical stimulation devices are now commonly used in medical practice. These devices provide periodic electrical stimulus, i.e., therapeutic pulses or shocks, to the heart or other organs to regulate the function of the stimulated organ. Implantable devices therefore, commonly employ leads for coupling an electrical pulse generator to excitable organ tissue.
Historically, the leads of a dual-chamber pacemaker, for example, are inserted transvenously within the right side of the heart. Under several circumstances, however, simultaneous pacing of both the right and the left sides of the heart may be desirable. For example, pacing both ventricles simultaneously may improve the clinical status and ventricular function of patients with congestive heart failure.
In these instances a transvenous endocardial lead, typically inserted through the coronary sinus and into one of the branches of the coronary venous system, is used to deliver pacing pulses or therapeutic shock to the left ventricle. Clinically, transvenous implantation is less invasive with reduced post-operative pain and associated trauma than other common lead implantation techniques.
However, in some patients, particularly children and patients with compromised coronary sinus veins, an external or epicardial lead may be medically indicated. The implantation of an external or epicardial lead historically required a mini thoracotomy or full sternotomy surgical procedure. Thoracic surgery, which typically involves the opening of the chest cavity to expose the patient's heart, is highly traumatic to the patient. The trauma associated with thoracic surgery may be especially severe for those patients with congestive heart failure and typically also necessitates considerable in-hospital recovery time for the patient.
However, the advent of thoracoscopy in cardiac surgery allows surgeons to implant epicardial leads percutaneously into the pericardial space. In these procedures, an epicardial lead is inserted into the pericardial space through a small opening in the chest cavity and a small incision or puncture in the pericardial sac.
In the past, epicardial leads were often sutured directly to the heart wall to secure the lead in place, increasing the complexity of the implant procedure. In addition, a larger introducer may be necessary to implant a lead having a suture pad into the pericardial space, resulting in a larger incision, more scarring, and potentially more post-operative pain for the patient.